Prep the pan: Grease your madeleine mold with butter and lightly dust with rice flour. Tap out the excess and set aside.
Whisk eggs and sugar: In a mixing bowl, beat the eggs and cane sugar for 3–5 minutes until pale, thick, and airy.
Add butter and flavor: Gently mix in the melted butter, vanilla, and lemon zest (if using).
Combine dry ingredients: In another bowl, whisk together almond flour, rice flour, tapioca starch, baking powder, xanthan gum (if using), and salt.
Fold it in: Gently fold the dry mixture into the wet batter using a spatula until just combined—do not overmix.
Rest the batter: Cover and refrigerate the batter for at least 30 minutes (or up to overnight) to help achieve the classic madeleine “hump.”
Bake: Preheat oven to 375°F (190°C). Spoon batter into prepared molds, filling each cavity about ¾ full. Bake for 10–12 minutes or until edges are golden and centers spring back.
Cool and finish: Let cookies rest in the pan for 2–3 minutes before transferring to a wire rack. Dust with powdered sugar before serving.
